The main problem associated with phosphates is over-fertilization of surface water, more commonly termed "eutrophication", referring to the "eutrophic" or enriched state of the water system. As a natural limiting nutrient, phosphate levels govern growth rates for vegetation, generally microscopic floating plants and algae (in particular blue-green algae which subsequently produces algal toxins). In water where other limiting nutrients or factors are low (such as nitrogen, silicate, temperature, and light), increase in phosphate levels may have little effect. However, where these other factors are sufficiently high, increasing phosphate levels will see immediate increases in biological growth and subsequent biological oxygen demand and also affect the pH balance of the water. This increased oxygen demand disturbs the delicate water ecosystem leading directly to fish kills and the growth of anaerobic bacteria.
Monitoring of phosphates levels, as released by industry, agriculture, and domestic sources, is essential for enforcement of regulations and imposition of limits. It also allows more accurate development of environmental models to determine the sources, fates, and risks associated with phosphates. Such monitoring occurs at point sources at the input and various treatment stages of water treatment plants, and throughout river and estuarine waterways. At a local level, individual catchment areas or river systems require regular monitoring to allow environmental scientists to determine past and predict future trends in phosphate levels. Regulatory agencies also depend upon accurate and regular data to identify isolated pollution incidents, particularly where legal action may follow.
Monitoring of phosphates also takes place within industry as part of environmental management and within processes that employ phosphate containing chemicals. Self-monitoring of nutrients in soils and run-off waters is also increasing within the agricultural sector.
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